When one is not equipped to write an objective biographical tribute
on the occasion of a great man's passing, all one can offer is one's own
personal recollection and appreciation.

When I enrolled in Psychology
21 at McGill University twenty-one
years ago, it was with the usual undergraduate expectation that Freudian
psychology was psychology, and that it would help you understand your own
mind and everyone else's. The instructor for this enormous introductory
course looked anything but Freudian. This gaunt maritimer called Hebb,
with his stern spectacles and portentous limp, who pronounced "calm" "cam,"
looked more qualified to teach us about practical seamanship than about
the mysteries of the psyche (although his tone was incongruously gentle,
sometimes even dreamy). He warned us from the outset that he was going
to wean us of our preconceptions about psychology. And so he did. Not all
at once, but gradually---with his emphasis on the role of our biological
heritage (through those unforgettable anecdotes about "Booie" and the other
chimps Hebb had worked with at Yerkes'
primate center) as well as our early experience (and experience in
general) in shaping those thought processes that we had all been so ready
to interpret symbolically in terms of old Greek myths recirculated in late
Victorian Vienna---he succeeded in distancing us at least from the inclination
to change courses in favor of something more like what we had been expecting.

For me, however, the transformation was unforgettable and very specific.
I can remember that when I was a child and people spoke of the "brain,"
I had always assumed that it was just a figure of speech. It seemed obvious
that my mind was not a material substance, so people couldn't really mean
it when they said that we had a physical organ that was responsible for
our minds in the same way that a heart was responsible for circulation
and a stomach for digestion. When I had learned that there really was a
brain, I just filed it away as a kind of oddity, never even tying it together
with my only other early contact with the
mind/body problem (one solipsistic summer).

But then Hebb reminded us of the problem anew, first through suggestive
accounts of his work with Penfield
on the localization of memories in the brain, and then from the viewpoint
of his own specific hypothesis that thoughts could actually be the activity
of reverberating circuits of neurons called "cell-assemblies." I don't
think his idea had its full impact on me at the moment he described it.
Rather, it was after the lecture, as I thought about it, and thought that
my thoughts may well consist of those physical things I was thinking about,
that I realized what a radically different world view such a theory represented,
and that it all had a ring of reality to it that made the Freudian notions
I had been flirting with sound like silly fairy tales. Here were the real
unconscious processes underlying our thinking, instead of the anthropomorphic
machinations of some Freudian "unconscious mind," which now began to look
rather like a supernumerary and supererogatory alter homunculus: One
mind/body problem was enough!

Then, almost before the revelation his hypothesis represented had had
a chance to take effect, Hebb took it back, informing us that his theory
was almost certainly wrong. What followed was his second revelation: That
a theory need not be right in order to be informative and to guide us in
the right direction. And the cell assembly theory (together with other
ideas in Hebb's epochal 1949 monograph, The Organization of Behaviour)
had indeed inspired an enormous wealth of research findings, from the effects
of sensory enrichment and deprivation to electrical and chemical pleasure
centers in the brain to theoretical
modeling of neural networks, as we went on to learn panoramically from
the rest of Psychology 21 (based, as it was, on Hebb's
Textbook
of Psychology, which was itself based largely on research inspired
and organized by his ideas).

Hebb himself was not only altogether unpretentious but also ever sceptical
about his ideas. He saw them as pointing the way toward answers, rather
than representing the answers themselves. In this I believe he had had
a veridical insight into the state of contemporary psychology: he did not
see much that was lapidary in it. A student of Karl Lashley,
whose own contribution had been mainly critical and heuristic, Hebb always
stated with complete conviction that he regarded B.
F. Skinner as the greatest psychologist of the century. This, despite
the fact that (in my opinion) Hebb's own work and the research it provoked
(rather than Chomsky's
celebrated review of Skinner's
Verbal
Learning) may well turn out to be seen historically as having provided
the real empirical alternative to behaviorism.

Contemporary cognitive science lays claim to a variety of roots (linguistic,
philosophical, computational), but it also takes a lot for granted. Without
any particular brief for symbolic representation, Hebb had been arguing
for four decades that thoughts are processes represented in the head, and
that behaviorism, in an over-reaction against introspectionism, was begging
the important questions in psychology. For Hebb, the business of scientific
psychology was to make inferences about the unobservable physical substrates
of behavior, thinking, personality and emotion. Such inferences were risky
(unlike behaviorism's reinforcement schedules), in that they might be very
wrong; but as long as they suggested testable predictions and successfully
guided research, they were leading toward the truth about the mind. Another
negative lesson Hebb had learned from behaviorism was that it is unwise
scientific practice to ignore anything, be it our brain, our biological
heritage, our cognition or our conscious experience. There is the room---indeed
the need---in Hebb's cognitive psychobiology for studying all of these.
And just as he avoided arbitrary dismissiveness and question-begging, Hebb
resisted any sense of premature closure, of already having found the answers.
(Contemporary cognitive science might do well to introspect somewhat as
to whether, in its own animistic interpretations of symbolic processes,
it has not inadvertently rejoined the
hermeneutic road to Vienna.)

Hebb may well have been taking the proper measure of his subject when
he declined the honor of having been its greatest contributor to date.
In my view, his tribute to Skinner expressed his conviction that whereas
theoretical ideas will come and go for some time to come in scientific
psychology, its methodological commitment to ultimate behavioral testability
(which is to say, empirical testability) is here to stay.

I went on to do honors psychology at McGill, and to write my honors
thesis under Hebb (the last thesis he supervised, to my knowledge), and
I continue to regard everything I do in psychology as Hebb-inspired. Many
people feel this way about their own personal intellectual debt to Hebb
(although "debt" is not really the right word---it's much more like "credit"),
especially McGill people. There is also a related tendency on the part
of the students of "D. O." (as Hebb was affectionately known locally) to
see all good things in psychology as having issued from him. Perhaps this
is a weakness of the students of all great teachers, and D. O. would certainly
have been the first to pooh-pooh it. But before I set it down to mere discipial
bias, I shall await the judgment of objective historians.

Historians have been relatively silent about D.O. so far, partly, no
doubt, out of deference for the fact that he was still alive. For his part,
D.O. had, in his wisdom, been electing to keep his own counsel in his last
years, declining the many invitations to pronounce on the past, present
and future of psychology that inevitably accrue to the grand old men of
a field. He abstained in part because he remained ever the shrewd and dispassionate
observer of life-cycle effects in his cognitive capacities (and those of
others). And in part it was out of the perennial modesty and scepticism
of this down-to-earth and very humane man.

But now that the old mariner's body has completed its last voyage, it
is time we evaluated in earnest the treasures left us by his mind.